[Sendgrid Audiences] - adding user attribute and custom field support

[joe-ayoub-segment]

Adding user attribute and custom_field support for Sendgrid Audience Destination.

Testing

Unit test added. Tested locally.
Not in use by customers yet.

[codecov]

Codecov Report

Attention: Patch coverage is 46.42857% with 15 lines in your changes missing coverage. Please review.

Project coverage is 78.51%. Comparing base (38940ff) to head (b7c59ef).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
.../sendgrid-audiences/syncAudience/dynamic-fields.ts	16.66%	10 Missing ⚠️
...tinations/sendgrid-audiences/syncAudience/utils.ts	66.66%	1 Missing and 3 partials ⚠️
...tinations/sendgrid-audiences/syncAudience/index.ts	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2604      +/-   ##
==========================================
- Coverage   78.57%   78.51%   -0.06%     
==========================================
  Files        1027     1028       +1     
  Lines       18121    18147      +26     
  Branches     3416     3422       +6     
==========================================
+ Hits        14238    14249      +11     
- Misses       2748     2760      +12     
- Partials     1135     1138       +3     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[joe-ayoub-segment]

We're in a deploy freeze so next deploy scheduled for 3-Dec

[joe-ayoub-segment]

deployed